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Finding the Fourth Proportional to 1,221.90, 1,686.24 and 717.90

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Solution

The fourth proportional to 1,221.90, 1,686.24 and 717.90 is: 990.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.90 : 1,686.24 = 717.90 : x
  2. Step 2: Convert to fraction form
    1,221.90/1,686.24 = 717.90/x
  3. Step 3: Cross multiply
    1,221.90x = 1,686.24 × 717.90
  4. Step 4: Simplify right side
    1,221.90x = 1,210,551.70
  5. Step 5: Solve for x
    x = 1,210,551.70/1,221.90
  6. Step 6: Final answer
    x = 990.71

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.